Hydrocarbon conversion process



H. BEUTHER ET AL HYDROCARBON CONVERSION PROCESS Filed Deo. 20, 1951 Oct. 9, 1956 United States 2,766,177 HYDROCARBON CONVERSION PROCESS Application December 20, 195'1, Serial No. 262,558 3 Claims. (Cl. 196-9) This invention relates to a hydrocarbon conversion process and more particularly, to a process for obtaining gas-oline from a high-boiling asphaltic petroleum hydrocarbon feed.

Among the problems facing the petroleum retiner is the cracking of asphaltic high-boiling petroleum feeds such as the so-called dirty gas oils, i. e., virgin gas oils containing significant quantities of asphalt, such as 2 to 3 percent or more, recycle and residual asphaltic gas oils from thermal and catalytic cracking processes, and topped ir reduced asphaltic crudes. It is highly desirable that high-boiling asphaltic petroleum hydrocarbon feeds such as the foregoing be treated to achieve the maximum degree of cracking conversion since with this type of feed, increased cracking severity generally produces both an increased yield of gasoline product and an improved octane number rating for the gasoline product. However, the asphaltic constituents of the feed are readily transformed into coke and other undesirable carbonaceous contaminants which tend to deposit upon the walls of the heating tubes and transfer lines, eventually plugging the system. For this reason, severe thermal cracking 'of asphaltic stocks is generally avoided.

Accordingly, this invention relates to a process for obtaining high octane gasoline in high yield from highboiling asphaltic petroleum hydrocarbon feeds such as those mentioned above. This process comprises contacting the high-boiling asphaltic petroleum hydrocarbon feed with normally gaseous hydrocarbons having 1 to 4 carbon atoms at a temperature of about 60 to 175 F. and a pressure sufcient to cause the Css- C4 gases (predominantly propane and propylene with some butanes and butenes) to be absorbed in the feed and preventtheir vaporization, usually of the order of 150 to 400 pounds per square inch gauge. The volatile nonabsorbed Cr-Cz gases are substantially removed as gaseous efuent. As a result of the contact, the asphaltic constituents of the feed are substantially separated from the remainder of the feed by being precipitated as a mixture comprising asphalt and Ca-C4 hydrocarbons. The liquid remainder comprising a mixture of deasphalted hydrocarbon feed and C13-C4 hydrocarbons is thermally cracked at an elevated temperature of about 975 to l100 F. and an elevated pressure of about 200 to 2000 pounds per square inch gauge to form a product containing gasoline, hydrocarbon constituents heavier than gasoline, and normally gaseous hydrocarbons having 1 to 4 carbon atoms. The presence of the Ca-C4 hydrocarbons materially assists the thermal cracking under the conditions stated above and reduces the formation of carbonaceous contaminants. ln addition, the Cs-C4 gases enter into thermal alkylation and polymerization reactions to form additional gasoline. The thermally cracked product is cooled and fractionated to separate the gasoline and heavier hydrocarbon constituents from the normally gaseous hydrocarbons. The normally gaseous hydrocarbons are then recycled for contact with further amounts of high-boiling asphaltic petroleum hydrocarbon feed and the process repeated.

Within the broad Contact temperature range of about Watent ICC 60 to 175 F. cited above as being useful in the deasphalting step, the temperature range of about to F. is preferred. Furthermore, the preferred thermal cracking temperature for the deasphalted feed mixture is about l030 to 1070 F. and the preferred cracking pressure is of the order of 1000 to 1500 pounds per square inch gauge. A broad range of Cir- C4 gas recycle ratios such as between about 100 and 400 volume per cent (the gas considered in the liquid form) of the feed may be utilized. Any surplus Ss-C4 gases above the desired recycle volume can be removed as gaseous etiluent with the Cr-Cz gases by adjusting the temperature and/or pressure in the deasphalting step.

The separated asphalt and Cs-C4 hydrocarbon mixture can be subjected to a variety of treatments. Thus the C3-C4 hydrocarbons can be removed, as by vaporization, and recycled for further contact with high-boiling asphaltic petroleum hydrocarbon feed, and the residual asphalt sold for uses such as road paving, construction, etc. However, in the preferred embodiment of our invention, the asphalt and C3-C4 hydrocarbon mixture is thermally cracked to produce a product comprising valuable liquid and gaseous hydrocarbons. This thermal cracking of the asphalt mixture can advantageously be accomplished at an elevated temperature of about 850 to 1000 F. and an elevated pressure of about to 1000 pounds per square inch gauge, with the preferred temperature being about 925 to 950 F. and the preferred pressure being about 200 to 400 pounds per square inch gauge. Paralleling the thermal cracking of the deasphalted feed, the presence of C3-C4 hydrocarbons materially assists the cracking of the asphalt to gasoline and reduces the formation of carbonaceous contaminants as well as providing additional valuable liquid products by alkylation and polymerization reactions. This thermally cracked product is combined with the product obtained from the thermal cracking of the deasphalted feed mixture and the combined cracked products then cooled and fractionated to` separate gasoline and heavier hydrocarbon constituents from the normally gaseous hydrocarbons. The normally gaseous hydrocarbons are recycled for further contact with feed as before. In this manner, an improved yield of gasoline and other valuable liquid hydrocarbons can be effected from high-boiling asphaltic feeds.

It is one of the features of our invention that the thermal cracking of the deasphalted feed and C3-C4 mixture, or in the preferred embodiment, of the deasphalted feed mixture and of the separated asphalt and C3-C4 mixture furnishes a sufficient quantity of C3-C4 hydrocarbons to provide for the facile deasphalting of the asphaltic feed and the thermal cracking of both the deasphalted feed mixture and separated asphalt mixture without the introduction of additional amounts of Ca--C4 hydrocarbons from extraneous sources. However, if such hydrocarbons are available from extraneous sources, they can be converted in part to gasoline by passing them through either cracking furnace of the instant process along with the normal charge.

As illustrative of the process of our invention, reference should be had to the accompanying ligure which is hereby incorporated into our application and made a part thereof. A high-boiling asphaltic petroleum hydrocarbon feed comprising a Thermofor Catalytic Cracking recycle gas oil stock containing a high percentage of asphalt and having the following inspection:

Gravity, API 22.2 Aniline point, F 157 Bromine number 9 Carbon residue, percent 0.44

Pour point, F 65 Sulfur, percent 0.36

ASTM distillation, i F. (vacuum corrected to 1By characterization factor is meant the value obtained from the cube root of the cubic average boiling point, in degrees Rankine, divided by the s ecic gravity at 60/60 F. (Seg Industrial and Engineering hemistry, vol. 29, page 1408. 193

is introduced into the system from line 10, feed pump 12, and line 14 into the upper portion of absorber 16. A recycle stream of normally gaseous hydrocarbons having 1 to 4 carbon atoms comprising mainly Cs--Oi hydrocarbons and predominantly C3 hydrocarbons is introduced near the base of absorber 16 from line 18 at a rate of 300 volume percent (the gas volume considered in the liquid form) of the feed. The feed within absorber 16 passes downwardly, countercurrent to the upwardly moving gaseous hydrocarbon stream at a temperature of about 110 F. and a pressure of about 300 pounds per square inch gauge. Under these conditions, most of the C3-C4 hydrocarbons are absorbed in the feed and the nonabsorbed low-boiling Ci-Cz hydrocarbon gases removed from the top of absorber 16 through line 13, valve 15, and line 17. The asphaltic constituents of the feed are precipitated and the precipitated asphalt removed in the form of a mixture comprising asphalt and C3-C4 hydrocarbons from the base of absorber 16 through line 2.0. The further treatment of this asphaltic mixture is given below.

The deasphalted liquid eiiluent from Iabsorber 16 coinprising a mixture of deasphalted feed and Cri-C4 hydrocarbons is removed through line 22 and passed to pressure pump 24. In pressure pump 24, the mixture is pressurized to a pressure of about 1500 pounds per square inch gauge. The pressurized mixture is then passed through line 26 into polyforming furnace 28 wherein it is thermally cracked to achieve a high degree of cracking conversion in the presence of Cs-CaA hydrocarbons (polyformed).

Polyforming furnace 28 is operated at a coil volume of 0.016 cubic feet above 750 F. per barrel throughput per day with a furnace outlet temperature of about 1030 to 1040 F. Under these conditions a degree of cracking conversion per pass of the feed considerably higher than could be effected if the feed were cracked in the presence of the asphalt, and substantially higher than could be effected if the feed were cracked in the absence of the C3-C4 hydrocarbons is achieved without encountering an excessive deposition of carbonaceous contaminants in the furnace coil. This higher degree of cracking conversion is reected, as has been indicated, by both an increased yield of gasoline and a marked improvement in the octane number of the gasoline. Concomitant with the high yield of gasoline, appreciable quantities of C3-C4 hydrocarbons are also obtained with but a minor amount of Ci-Cz hydrocarbons.

The effluent from polyforming furnace 2S is removed through line 32 and is cooled by admixture with cooled pressurized quench from line 30 to a temperature of about 6000 F. The combined mixture is then depressurized by passing through depressurizing valve 34 to a pressure somewhat above 300 pounds per square inch gauge. It is necessary that the pressure after depressurizing valve 34 be somewhat above the pressure in absorber 16 so as to maintain a flow head pressure throughout the system.

The depressurized mixture is passed through line 36 to separator 38. A temperature differential is maintained within separator 38, with the base of the separator being at a temperature of about 600 F., and the top of the separator through line 40, and the gasoline and normally manner, the fuel oil and liquid hydrocarbon constituents Cil heavier than gasoline are withdrawn at the base of the separator through line 40, and the gasoline and normally gaseous hydrocarbons are Vwithdrawn overhead through line 42. A portion of the withdrawn fuel oil bottoms from line 40 is recirculated as quench through line 44, valve 46, line 48, and pressurizing pump 50. In pressurizing pump 50, this quench is pressurized to the polyforming pressure of 1500 pounds per square inch gauge and then passed through line 52 into cooler 54. Within cooler 54, the quench is cooled to a temperature of about 450 F. Cooled quench is then passed through line 30 from which it is admixed with the effluent from polyforming furnace 28 in line 32.

The overhead from separator 38 in line 42, comprising gasoline and lighter hydrocarbons, is passed to stabilizer fractionating column 56. The gasoline portion of this overhead is removed from the base of stabilizer fractionating column 56 through line 53. A sufficient amount of C4 hydrocarbons is retained in the gasoline removed through line 58 to provide a satisfactory Reid vapor pressure therefor. The low-boiling normally gaseous hydrocarbons are removed overhead from stabilizer fractionating column 56 at a temperature of about 125 F. and are recycled through line 18 for further contact with the feed in absorber 16.

The asphaltic mixture in line 20 comprising asphalt and C3-C4 hydrocarbons can, as has been indicated heretofore, be subjected to a variety of treatments. Thus, the Ca-C4 hydrocarbons can be removed by flash distillation in a iash chamber (not shown) and recycled through line 18 for further contact with the feed in absorber 16. The residual asphalt can then be sold as a paving or construction material. Preferably, however, the asphaltic mixture is cracked. This is advantageously accomplished by the procedure shown in the figure. Thus, the asphaltic mixture is passed through pressure pump 60 and is pressurized to a pressure of about 400 pounds per square inch gauge. The pressurized mixture is then passed through line 62 to asphalt furnace 64. A furnace outlet temperature of 925 F. and a coil volume of 0.020 cubic feet above 750 F. per barrel throughput per day is maintained in asphalt furnace 64. Under these conditions the asphalt and (s-C4 hydrocarbon mixture is cracked and yields gasoline and valuable liquid and gaseous hydrocarbons. The cracked product is withdrawn from asphalt furnace 64 through line 66 and depressurizing valve 68. In depressurizing valve 68, the cracked product is depressurized to a pressure equal to that within line 36, somewhat above 300 pounds per square inch gauge. From depressurizing valve 68, the cracked asphaltic products pass through line 70 into cooler 72 wherein the cracked products are cooled to a temperature of about 600 F. The cooled cracked asphaltic products are then passed through line 74 and combined with the cracked polyforming product in line 36.

It is obvious that our invention may be modified by one skilled in the art, and it is to be understood that these modifications which are readily apparent to one skilled in the art are included within our invention and made a part of the appended claims. By way of example, these modifications include varying process variables such as temperature, pressure, recycle gas dilution, etc. in accordance with the established practice Within the polyforrning art. Furthermore, portions of the cracked products from polyforming furnace 2S or asphalt furnace 64, such as the fuel oil removed from the base of separator 38 through line 40 may be recycled for further cracking conversion. However, it is usually not desirable to recycle the cracked products from our process since we are able to obtain such deep conversion of the feed as to render recycling economically inadvisable.

Due to the increase in the severity with which heavy asphaltic oils may be cracked if the asphaltic constituents are removed, the process of our invention furnishes a greatly increased yield of gasoline over that which is obtained when the entire asphaltic feed is passed to the polyforming furnace. Thus, when an asphaltic reduced crude is employed as the process feed, a yield increase of as much as 200 percent or more of product gasoline can be obtained. Even with the so-called dirty gas oils, a 25 percent increase in gasoline yield can be effected. Furthermore, there is a marked increase in the octane rating of the gasoline product obtained through the application of our process. Thus, an increase of as much as octane numbers in the octane rating of the gasoline product can be effected when employing an asphaltic reduced crude as the process feed, and an increase of as much as 5 octane numbers in the case of a dirty gas oil feed.

In addition to the foregoing, a marked improvement in the ease of process operation is achieved. Thus, it is possible to charge highly asphaltic feeds for sustained periods of operation without incurring the excessive coke deposition which would otherwise result from attempts to crack such feeds.

We claim:

1. A process for obtaining gasoline from a high-boiling asphaltic petroleum hydrocarbon feed which comprises contacting said feed with a fraction comprising gaseous hydrocarbons having 1 to 4 carbon atoms at a temperature of about 60 to 175 F. and a pressure within the range of 150 to 400 pounds per square inch gauge suiiicient to maintain the normally gaseous hydrocarbons having 3 to 4 carbon atoms absorbed in the feed and prevent their vaporization, removing the volatile gaseous hydrocarbons having 1 to 2 carbon atoms, separating a precipitated mixture comprising asphalt and normally gaseous hydrocarbons having 3 to 4 carbon atoms from a liquid mixture comprising deasphalted feed and normally gaseous hydrocarbons having 3 to 4 carbon atoms, thermally cracking said liquid mixture at a temperature of about 975 to 1100 F. and a pressure of about 200 to 2000 pounds per square inch gauge to form a product containing gasoline, hydrocarbon constituents heavier than gasoline, and normally gaseous hydrocarbons having 1 to 4 carbon atoms; separately thermally cracking said mixture comprising asphalt and normally gaseous hydrocarbons having 3 to 4 carbon atoms at a temperature of about 850 to l000 F. and a pressure of about 150 to 1000 pounds per square inch gauge to form a product comprising normally liquid and normally gaseous hydrocarbons, combining this thermally cracked product with the product obtained from the thermal cracking of the deasphalted feed mixture, cooling and fractionating the combined products to separate the gasoline and heavier hydrocarbon constituents from the normally gaseous hydrocarbons, and recycling the normally gaseous hydrocarbons for contact with an additional amount of high-boiling asphaltic petroleum hydrocarbon feed.

2. A process for obtaining gasoline from a high-boiling asphaltic petroleum hydrocarbon feed which comprises contacting said feed with a fraction comprising gaseous hydrocarbons having 1 to 4 carbon atoms at a temperature of about 100 to 140 F., a ratio of the volume, as liquid, of ythe hydrocarbons having 1 to 4 carbon atoms to the volume of the feed in the range of about 1:1 to 4:1 and a pressure within the range of 150 to 400 pounds per square inch gauge sucient tto maintain the normally gaseous hydrocarbons having 3 to 4 carbon atoms absorbed in the feed and prevent their vaporization, removing the volatile gaseous hydrocarbons, having 1 to 2 carbon atoms, separating a precipitated mixture comprising asphalt and normally gaseous hydrocarbons having 3 `to 4 carbon atoms from a liquid mixture comprising deasphalted feed and normally gaseous hydrocarbons having 3 -to 4 carbon atoms, pressurizing said liquid mixture to a pressure of about 1000 to 1500 pounds per square inch gauge, thermally cracking said pressurized mixture at a `temperature of about 1030 to 1070 F. to form a product containing gasoline, hydrocarbon constituents heavier than gasoline, and normally gaseous hydrocarbons having 1 to 4 carbon atoms, depressurizing said product to a pressure within the range of and 400 pounds per square inch gauge; separately thermally cracking said mixture comprising asphalt and normally gaseous hydrocarbons having 3 to 4 carbon atoms at a temperature of about 925 to 950 F. and a pressure of about 200 to 400 pounds per square inch gauge to form a product comprising normally liquid and normally gaseous hydrocarbons, adjusting the pressure on this product to a pressure equal yto the pressure of the depressurized product obtained from the thermal cracking lof the deasphalted feed mixture quenching the product from the thermal cracking of the deasphalted feed and normally gaseous hydrocarbons to a temperature below the temperature of cracking of the asphalt, combining the two thermally cracked products, cooling and fractionating the combined pnoducts to separate the gasoline and heavier hydrocarbon constituents from the normally gaseous hydrocarbons, and recycling the normally gaseous hydrocarbons for contact with an additional amount of high-boiling asphaltic petroleum hydrocarbon feed.

3. A process for obtaining gasoline from a high-boiling iasphaltic petroleum hydrocarbon feed which comprises contacting said feed with a fraction comprising gaseous hydrocarbons having 1 to 4 carbon atoms at a temperature and pressure suicient to maintain the normally gaseous hydrocarbons having from 3 to 4 carbon atoms absorbed in the feed and prevent their vaporization, removing volatile gaseous hydnocarbons having 1 to 2 carbon atoms, separating a precipitated mixture comprising asphalt and normally gaseous hydrocarbons having 3 to 4 carbon atoms from a liquid mixture comprising deasphalted feed and normally gaseous hydrocarbons having 3 to 4 carbon atoms, thermally cracking said liquid mixture at an elevated temperature and pressure Ito form a product containing gasoline, hydrocarbon constituents heavier than gasoline, and normally gaseous hydrocarbons having l to 4 carbon atoms, separately thermally cracking said mixture comprising asphalt and normally gaseous hydrocarbons having 3 to 4 carbon atoms at an elevated temperature and pressure to form a product comprising normally liquid and normally gaseous hydrocarbons, quenching the product from the thermal cracking of the deasphalted feed mixture to a temperature lower than that employed in the thermal cracking of the asphalt-containing mixture, combining the thermally cracked product from the asphalt-containing mixture with the quenched product from the thermal cracking of :the deasphalted feed mix-ture, cooling and fractionating the combined pnoducts to separate the gasoline and heavier hydrocarbon constituents from the normally gaseous hydrocarbons, and recycling the normally gaseous hydrocarbons for contact with an additional amount lof high-boiling asphaltic petroleum hydrocarbon feed.

References Cited inthe file of this patent UNITED STATES PATENTS OTHER REFERENCES Sachanen: Conversion of Petroleum, Reinhold lishing Corp., 330 W. 42nd Street, New York, York (1940), pages 198 and 199.

Pub- New 

1. A PROCESS FOR OBTAINING GASOLINE FROM A HIGH-BOILING ASPHALTIC PETROLEUM HYDROCARBON FEED WHICH COMPRISES CONTACTING SAID FEED WITH A FRACTION COMPRISING GASEOUS HYDROCARBONS HAVING 1 TO 4 CARBON ATOMS AT A TEMPERATURE OF ABOUT 60* TO 175* F. AND A PRESSURE WITHIN THE RANGE OF 150 TO 400 POUNDS PER SQUARE INCH GAUGE SUFFICIENT TO MAINTAIN THE NORMALLY GASEOUS HYDROCARBONS HAVING 3 TO 4 CARBON ATOMS ABSORBED IN THE FEED AND PREVENT THEIR VAPORIZATION, REMOVING THE VOLATILE GASEOUS HYDROCARBONS HAVING 1 TO 2 CARBON ATOMS, SEPARATING A PRECIPITATED MIXTURE COMPRISING ASPHALT AND NORMALLY GASEOUS HYDROCARBONS HAVING 3 TO 4 CARBON ATOMS FROM A LIQUID MIXTURE COMPRISING DEASPHALTED FEED AND NORMALLY GASEOUS HYDROCARBONS HAVING 3 TO 4 CARBON ATOMS, THERMALLY CRACKING SAID LIQUID MIXTURE AT A TEMPERATURE OF ABOUT 975* TO 1100* F. AND A PRESSURE OF ABOUT 200 TO 2000 POUNDS PER SQUARE INCH GAUGE TO FORM A PRODUCT CONTAINING GASOLINE, HYDROCARBON CONSTITUENTS HEAVIER THAN THE GASOLINE, AND NORMALLY GASEOUS HYDROCARBONS HAVING 1 TO 4 CARBON ATOMS; SEPARATELY THERMALLY CRACKING SAID MIXTURE COMPRISING ASPHALT AND NORMALLY GASEOUS HYDROCARBONS HAVING 3 TO 4 CARBON ATOMS AT A TEMPERATURE OF ABOUT 850* TO 1000* F. AND A PRESSURE OF ABOUT 150 TO 1000 POUNDS PER SQUARE INCH GAUGE TO FORM A PRODUCT COMPRISING NORMALLY LIQUID AND NORMALLY GASEOUS HYDROCARBONS, COMBINING THIS THERMALLY CRACKED PRODUCTT WITH THE PRODUCT OBTAINED FROM THE THERMAL CRACKING OF THE DEASPHALTED FEED MIXTURE, COOLING AND FRACTIONATING THE COMBINED PRODUCTS TO SEPARATE THE GASOLINE AND HEAVIER HYDROCARBON CONSTITUENTS FROM THE NORMALLY GASEOUS HYDROCARBONS, AND RECYCLING THE NORMALLY GASEOUS HYDROCARBONS FROM CONTACT WITH AN ADDITIONAL AMOUNT OF HIGH-BOILING ASPHALTIC PETROLEUM HYDROCARBON FEED. 